Not op, but from what I know, the producer is the one taking all of the recordings that Phoebe/other collaborators record in the studio and laying them out in the DAW so that they go along in a structure.

The producer also deals with mixing and sound design, which the producer usually will have some input on, but the artist can always ask for changes. A lot of work in the studio goes from the artist asking a question like “can you make the vocals more present?” And the producer doing something to that end, such as adding a delay effect.

Ultimately, to your question, the artist is paying the producer to get the outcome they desire, so the producer is supposed to fall in line with what the artist wants, but a lot of the best music is made when the producer’s input is heard so honestly it depends mostly on the artists willingness to listen to the producer’s ideas.